The invention relates to a housing for biometric sensor chips.
Biometric sensor chips are being increasingly used for identity recognition, for example, for cash dispensers, for stocks and shares and/or for capital transfers through electronic media, or for recognizing access authorizations to bank accounts and databanks or else to other data records that are dependent on access authorizations. For such a purpose, in contrast to housings for microelectronic standard semiconductor chips, the housing for biometric sensor chips must have an area in which a fingerprint checking area of the biometric sensor chip is freely accessible. On the other hand, it is necessary to prevent the sensor chip from being destroyed, for example, as a result of electrostatic charging of a fingertip, as a result of a spark discharge when the fingerprint checking area is touched. Such a configuration should advantageously allow automatic mass production in a cost-effective manner based upon the rising demand for such housings with biometric sensor chips.
It is accordingly an object of the invention to provide a housing for biometric sensor chips that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that, for appliances and systems in which access is controlled by a pin number, such as cash dispensers, mobile telephones, and computers, provides such a housing for biometric sensor chips, in which the active structure of the sensor chip points outward on the appliance or system so that the operator can place a finger directly on the sensor chip, and to provide an economic manufacturing method for fitting such housings for biometric sensor chips.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a housing for chips, including at least one biometric sensor chip having a freely accessible fingerprint checking area and a ground contact surface, a mount substrate having contact outer surfaces, the mount substrate being a mounting strip with perforated edges, a housing frame disposed at the mount substrate, the contact outer surfaces being disposed on the mount substrate partially outside the housing frame, the sensor chip disposed within the housing frame, and the ground contact surface of the sensor chip being connected to the housing frame to form a ground frame.
A housing according to the invention for biometric sensor chips includes a freely accessible fingerprint checking area on the sensor chip, a mount substrate, and an outer contact surface on the mount substrate and has the advantage that it can be manufactured in large quantities using simple technology on a mount substrate that forms a mounting strip with perforated edges. The outer contacts can be disposed partially outside a housing frame on the mounting strip, and the sensor chip may be positioned within the housing frame. To protect the sensor chip, the housing frame is electrically connected to a ground contact surface of the sensor chip in order to form a ground frame that, like a lightning conductor, dissipates electrostatic charges on a fingertip away from the sensitive fingerprint checking area so that the electrostatic charge can be discharged through the ground frame without endangering the sensor chip.
For such a purpose, the housing frame is preferably produced from an electrically conductive material, or is at least coated with an electrically conductive material. The electrically conductive bushings for the outer contacts to the interior, which is surrounded by the housing frame, are electrically insulated from the housing frame so that it is impossible for a short circuit to occur between the outer contacts through the housing frame. The outer contacts may be disposed on the upper face of the mount substrate, which is also fitted with the sensor chip, or on the opposite lower face of the mount substrate.
In accordance with another feature of the invention, if the outer contacts are disposed in a preferred manner on the lower face of the mount substrate, then they are connected through bonding openings in the mount substrate and bonding wires to the contact surfaces of the sensor chip, which is disposed on the upper face of the mount substrate.
In accordance with a further feature of the invention, if the outer contacts are disposed in a preferred manner on the upper face of the mount substrate, on which the sensor chip is also provided, then bonded wires can advantageously be connected between the contact surfaces on the sensor chip through contact connecting surfaces of the contact outer surfaces, directly without any bonding openings in the mount substrate.
In accordance with an added feature of the invention, the mount substrate has a chip side, the sensor chip is connected to the chip side, and the contact outer surfaces are disposed on the chip side.
In accordance with an additional feature of the invention, the contact surfaces of the sensor chip and the contact outer surfaces of the mount substrate are disposed on an edge of the sensor chip or of the mount substrate so that short and uniformly spaced bonding connections are possible by bonding wires, and so that bonding of the sensor chips, which are installed in advance on the mount substrate, and of the associated contact outer surfaces can be carried out quickly, easily and uniformly because all the bonding connections have the same shape and the same length.
In accordance with yet another feature of the invention, the contact outer surfaces are located along one of the perforated edges of the mounting strip. Such a housing configuration makes it possible to use epoxy mounting strips, such as those that can also be used for smart card module manufacture. The mounting of the components together with the housing according to the invention into corresponding end appliances and end systems can be carried out as an SMT mounting process or, universally, with a flexible circuit fitting for making contact through connectors. The perforation in the edges of the mounting strip may for such a purpose be provided with a standard perforation in which, in one preferred development of the invention, the ground contact surface of the sensor chip is electrically connected to the housing frame through a structured metal coating on the mounting strip so that a grounded ground frame can be produced, which, at the same time, grounds the sensor chip.
In accordance with yet a further feature of the invention, the structured metal coating of the mounting strip can be produced by structuring of metal plating on the mounting strip. During such structuring process, the ground contact connections between the housing frame and the sensor chip and the connections for the outer contact surfaces can be prepared at the same time. For such a purpose, the structured metal coating preferably has contact outer surfaces that lead from the inside of the housing frame to the outside of the housing frame, are provided with bonding wires within the housing frame, and are freely accessible for further plug connections outside the housing frame.
In accordance with yet an added feature of the invention, the mounting strip has a structured metal coating of an insulating material and the sensor chip has a ground contact surface electrically connected to the housing frame through the structured metal coating.
To prevent a short circuit between the contact outer surfaces, the electrically conductive housing frame is mounted on the substrate mount in the area of the contact outer surfaces by an insulating adhesive, and, in the rest of the area of the substrate mount, is electrically connected to the ground contact surface of the sensor chip through a conductive adhesive. This variation in the type of adhesive allows all the areas of the housing frame to be fixed on the differently structured metal coating of the mount substrate.
In accordance with yet an additional feature of the invention, housing frame may substantially form a ground protection ring around the sensor chip or, at the same time, can be prepared for further mounting in an appliance or system. For such a purpose, the housing frame is formed from a ground frame with mounting openings, with the ground frame being fitted over a sufficiently wide area and in a sufficiently robust manner around the sensor chip so that, without needing to mechanically load the sensor chip, the ground frame can be screwed to an end appliance or an end system through the mounting openings, in an advantageous manner.
In accordance with again another feature of the invention, to further improve the safety for the sensor chip, it may preferably be covered by a conductive additional cover outside the fingerprint checking areas. The additional cover bridges the gap between the edges of the sensor chip and the ground frame. In a further preferred embodiment of the invention, the fingerprinting surface on the sensor chip may have a metal coating that is in the form of a frame and can preferably be connected to ground through the additional cover so that, outside the fingerprint checking area, the sensor chip is protected by a covering ground cover.
In accordance with again a further feature of the invention, both functions of the housing, namely of providing a housing frame as ground frame and of forming a ground cover, can preferably be carried out by a single deep-drawn or thermoformed part. A deep-drawn or thermoformed part such as this is placed over the sensor chip like a cup or a dish, which has no bottom so that the fingerprint checking area remains free in the open bottom area of the cup or dish.
In accordance with again an added feature of the invention, the mounting strip and/or ground frame of the housing may have the energy storage capacitors that are required for operation of the sensor chip, which, protected by the mounting strip and/or by the housing frame, are, thus, available for mounting in an appliance or system.
In accordance with again an additional feature of the invention, the mounting strip may be in the form of an endless strip, and may be composed of a polyimide film. In further preferred embodiments, the mount substrate is also produced from epoxy resin or is composed of a flexible polymer. This has the advantage that the sensor chips can be mounted and tested with the housing fitted in endless strips or blanks, and that the module mounting process can now be carried out in assembly lines that can also be used for smart card modules. Furthermore, the housing that is mounted on endless strips allows installation of the sensors to be easily integrated in the production process for the end appliances and end systems so that the installation process can accordingly be carried out cost-effectively.
In accordance with still another feature of the invention, the flexible circuits of the housings for the end appliances and end systems can be connected through plug connections such as zero-force connectors or through a soldered joint so that the connection technology to the housing according to the invention can be matched completely to the customer-specific production process. This also applies to the width, length, and shape of the connections on the substrate mount. The various variants of the ground frame mentioned above may be configured differently within the scope of the invention so that the ground frame is either in the form of a molding on the frame using a conductive fixed cover or is mounted in an electrically conductive manner to the frame or to the ground connection. However, the ground frame may also be fitted to the sensor chip by a conductive sheet or conductive covering compound. In this case, contact can be made with the ground connection of the sensor chip through the frame.
In accordance with still a further feature of the invention, the contact outer surfaces are disposed on the mount substrate partially inside the housing frame.
With the objects of the invention in view, there is also provided a housing for biometric sensor chips each having a ground contact surface, including a mount substrate being formed as a mounting strip with perforated edges, a housing frame disposed at the mount substrate for receiving at least one biometric sensor chip therein and defining a freely accessible fingerprint checking area for direct access by a user to the at least one biometric sensor chip, the mount substrate having contact outer surfaces disposed thereon partially outside the housing frame, and the housing frame is to be electrically connected to the ground contact surface of the at least one biometric sensor chip to form a ground frame.
The housing according to the invention is distinguished by a simple construction on an epoxy mount, on which the sensor chip can be offered to the customer in a manner that is advantageous for further processing. The special features, which are provided by the externally accessible active surface of a biometric sensor housing and the ground frame with the invention, simplify the production of the end appliances and end systems.
With the objects of the invention in view, there is also provided a method for producing a biometric sensor housing, including the steps of providing a housing frame and at least one sensor chip having contact surfaces and a ground contact surface forming a lower face of the sensor chip, structuring a metal coating on a mount substrate to form ground connecting surfaces in an area of the sensor chip, ground connecting surfaces in an area of the housing frame, and contact outer surfaces, perforating edges of the mount substrate, fitting the ground contact surface of the sensor chip onto the structured metal coating in the area of the ground connecting surfaces for the sensor chip, bonding the contact surfaces on the sensor chip to the contact outer surfaces on the mount substrate, fitting the housing frame onto the structured metal coating in the area of the ground connecting surfaces for the housing frame, and selectively sealing the bonded connections with a plastic encapsulation compound to produce a biometric sensor housing having at least one sensor chip and a freely accessible fingerprint checking area on the sensor chip.
Such a method has the advantage that it is suitable for mass production of housings for biometric sensor chips and allows immediate further processing of the housings with biometric sensor chips for production of cash dispensers, mobile telephones, and/or computers, access to which is allowed through a fingerprint.
In accordance with still an added mode of the invention, the sensor surface that is not used for fingerprint checking is covered by a housing cover, preferably, after the sealing step. Such a housing cover advantageously seals the edge area of the sensor chip hermetically against external influences so that only the fingerprint checking area remains freely accessible.
In accordance with still an additional mode of the invention, a sensor chip is provided having a ground contact surface in the form of a frame on the upper face of the sensor chip so that not only is it possible for the lower face of the sensor chip to be connected to ground, but an additional ground contact surface is also provided on the upper face of the sensor chip, in order to be short-circuited into the ground frame of the housing. Such a configuration has the advantage that it provides a relatively high degree of confidence that electrostatic discharges can be kept away from the central exposed fingerprint checking area. At the same time, the configuration also makes it possible to increase the life of the sensor chip in the housing according to the invention.
For such a purpose, the surface that is not used for fingerprint checking is preferably provided with an electrically conductive housing additional cover, which is connected to the ground contact connection on the upper face of the sensor chip. The entire housing including the cover thus forms protection, at ground potential, for the sensitive fingerprint checking area of the sensor chip. The cavities that are formed between the housing frame and the housing additional cover are, in accordance with another mode of the invention, filled with filler composed of plastic. Such a configuration has the advantage of making it possible to considerably increase the vibration resistance of the housing.
In accordance with a further mode of the invention, the metal coating on the mount substrate is structured by laser erosion. In such a variant, the mounting strip and the metal coating located on it can be tailor-made precisely and quickly in accordance with the requirements for the housing for a biometric sensor, using a continuous flow method.
In accordance with an added mode of the invention, the metal coating is structured by a photolithographic method. To perform such structuring, a photosensitive layer is applied to the metal coating of the mount substrate and the layer is, then, partially cured in an exposure step so that, in a further development step, the unexposed points can be dissolved away, and the metal of the coating located underneath can be removed by an etching process. Finally, the photoresist layer is removed from the remaining metal, preferably, by plasma incineration or ion bombardment. The application of a structuring protective layer over the metal layer for etching a structure may preferably also be achieved by a stencil-printing method or by a screen-printing method.
In accordance with a concomitant feature of the invention, the housing frame is preferably mounted on the substrate mount by an adhesive bonding technique, with the adhesive being applied in an electrically conductive or electrically insulating manner to the mount substrate or to the metal coating, respectively. Where the structured metal coating produces a short circuit to the ground contact surface of the sensor chip, an electrically conductive adhesive is used for mounting of the housing frame, in conjunction with the ground connection, to produce a ground frame for protection of the fingerprint checking area of the sensor chip. A soldering method is preferably also used as an electrically conductive connection between the ground frame and the metal coating on the mount substrate, in which soldering method a low melting point solder coating is additionally applied to the metal coating in the area of the housing frame on the mount substrate.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a housing for biometric sensor chips, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.